Yes. If you are a large organization and have the money for licenses and DBAs, they're definitely worth it.
Not everyone is a startup. Not everyone cares about clever hacks and rag-tag scalability and bragging about how they scaled up to 10k transactions per second on YouTube. Sometimes you just want to throw $10M at the fucking thing and have it work so everyone in your company gets the data they need.
I also think there are established communities (and codebases) that have existed for decades built around some of these products (like Oracle or DB2 on the mainframe). This is also a consideration for many organizations large and small.
I'm not saying that the open source solutions can't be competitive from a technological standpoint, simply that they have to win on cost, availability of experienced people for dev and admin, and overcome what amounts to a late start in the market.
Plus, on the low end of the market, aren't there express editions of SQL Server and Oracle available for free? For lightweight use these would seem to be reasonable competitors to open source.
I think this is a huge part of the issue. I have worked professionally on the big three commercial rdbms (DB2 distributed - not mainframe -, SQL Server, and Oracle). I consider myself a SQL hacker with some DBA experience and knowledge, mainly around DB design and performance tuning.
I simply don't care what rdbms I coding to, I can tweak to leverage quirkiness in T-SQL or PL/SQL if needed or advantageous to a project. And, <whispering>, PL/pgSQL.
A common experience for me when job searching is to apply for a job where, for example, they are primarily looking for Oracle PL/SQL development. I've been doing SQL coding for roughly 8 years, the last 2 years or so have been primarily in Oracle PL/SQL. I have been turned down for interviews with feedback that says "oh, we need someone with 5 years of Oracle development work."
If it's techies doing the resume reviews, I always get at least an interview. Sometimes even then, I have to sell the fact that SQL skills transfer nicely between rdbms harder than I should.
Not everyone is a startup. Not everyone cares about clever hacks and rag-tag scalability and bragging about how they scaled up to 10k transactions per second on YouTube. Sometimes you just want to throw $10M at the fucking thing and have it work so everyone in your company gets the data they need.